Leuprolide acetate is an LHRH agonist analog that is useful in the palliative treatment of hormonal related prostate cancer, mammary cancer, endometriosis, and precocious puberty. With continued use, leoprolide acetate causes pituitary desnsitizing and down-regulation to affect the pituitary-gonodal axis, leading to suppressed circulating levels of luteinizing and sex hormones. In patients with advanced prostate cancer, achieving circulating testosterone levels of less than or equal to 0.5 ng/ml (chemical castration level) is a desired pharmacological indicator of therapeutic action.
Originally, leuprolide acetate was launched in the United States as a daily subcutaneous (s.c.) injection of the analog solution. The inconvenience of chronic repetitive injections was later eliminated by the development of a one month sustained release depot product based on poly(DL-lactide-co-glycolide) microspheres (Lupron(copyright) Depot). Currently, one, three, and four month formulations are widely available as intramuscular (i.m.) injections of microspheres.
Although the current Lupron(copyright) Depot microspheres appear to be effective, the microsphere products are difficult to mnanufacture, and they all require a deep intramuscular (i.m.) injection using large volumes of fluid to ensure that all of the microspheres are properly administered to the patient. These injections are often painful and lead to tissue damage.
Biodegradable polymers other than Lupron(copyright) Depot have been employed in many medical applications, including drug delivery devices. The drug is generally incorporated into the polymeric composition and formed into the desired shape outside the body. This solid implant is then typically inserted into the body of a human, animal, bird, and the like through an incision. Alternatively, small discrete particles composed of these polymers can be injected into the body by a syringe. Preferably, however, certain of these polymers can be injected via syringe as a liquid polymeric composition.
Liquid polymeric compositions useful for biodegradable controlled release drug delivery systems are described, e.g., in U.S. Pat. Nos. 4,938,763; 5,702,716; 5,744,153; 5,990,194; and 5,324,519. These compositions are administered to the body in a liquid state or, alternatively, as a solution, typically via syringe. Once in the body, the composition coagulates into a solid. One type of polymeric composition includes a nonreactive thermoplastic polymer or copolymer dissolved in a body fluid-dispersible solvent. This polymeric solution is placed into the body where the polymer congeals or precipitatively solidifies upon the dissipation or diffusion of the solvent into the surrounding body tissues. It is expected that these compositions would be as effective as Lupron(copyright) Depot, since leuprolide of these compositions is the same as are in the Lupron(copyright) Depot and the polymers are similar.
Surprisingly, however, it has been discovered that the liquid polymeric compositions according to the present invention are more effective in delivering leuprolide acetate than Lupron(copyright) Depot. Specifically, the testosterone levels obtained with the liquid polymeric compositions of the present invention containing the leuprolide acetate are lower at extended times in dogs compared to Lupron(copyright) Depot, and also at the six month point in humans, compared to the value reported in the literature for Lupron(copyright) Depot (Sharifi, R., J. Urology, Vol. 143, Jan., 68 (1990)).
The present invention provides a flowable composition that is suitable for use as a controlled release implant of leuprolide acetate. The flowable composition includes a biodegradable thermoplastic polyester that is at least substantially insoluble in an aqueous medium or body fluid. The flowable composition also includes a biocompatible polar aprotic solvent. The biocompatible polar aprotic solvent can be an amide, an ester, a carbonate, a ketone, an ether, or a sulfonyl. The biocompatible polar aprotic solvent is miscible to dispersible in aqueous medium or body fluid. The flowable composition also includes leuprolide acetate. The leuprolide acetate is preferably present in about 2 wt. % to about 4 wt. % of the composition or in about 4 wt. % to about 8 wt. % of the composition. Preferably, the flowable composition is formulated as an injectable subcutaneous delivery system. The injectable composition preferably has a volume of about 0.20 mL to about 0.40 mL or about 0.30 mL to about 0.50 mL. The injectable composition is preferably formulated for administration about once per month, about once per three months, or about once per four months to about once per six months. Preferably, the flowable composition is a liquid or a gel composition, suitable for injection into a patient.
Preferably, the biodegradable thermoplastic polyester is a polylactide, a polyglycolide, a polycaprolactone, a copolymer thereof, a terpolymer thereof, or any combination thereof. More preferably, the biodegradable thermoplastic polyester is a polylactide, a polyglycolide, a copolymer thereof, a terpolymer thereof, or a combination thereof. More preferably, the suitable biodegradable thermoplastic polyester is 50/50 poly (DL-lactide-co-glycolide) having a carboxy terminal group or is 75/25 poly (DL-lactide-co-glycolide) with a carboxy terminal group that is protected. The suitable biodegradable thermoplastic polyester can be present in any suitable amount, provided the biodegradable thermoplastic polyester is at least substantially insoluble in aqueous medium or body fluid. The suitable biodegradable thermoplastic polyester is preferably present in about 30 wt. % to about 40 wt. % of the flowable composition or is present in about 40 wt. % to about 50 wt. % of the flowable composition. Preferably, the biodegradable thermoplastic polyester has an average molecular weight of about 23,000 to about 45,000 or about 15,000 to about 24,000.
Preferably, the biocompatible polar aprotic solvent is N-methyl-2-pyrrolidone, 2-pyrrolidone, N, N-dimethylformamide, dimethyl sulfoxide, propylene carbonate, caprolactam, triacetin, or any combination thereof. More preferably, the biocompatible polar aprotic solvent is N-methyl-2-pyrrolidone. Preferably, the polar aprotic solvent is present in about 60 wt. % to about 70 wt. % of the composition or is present in about 45 wt. % to about 55 wt. % of the composition.
The present invention also provides for a method for forming a flowable composition. The flowable composition is useful as a controlled release implant. The method includes mixing, in any order, a biodegradable thermoplastic polyester, a biocompatible polar aprotic solvent, and leuprolide acetate. These ingredients, their properties, and preferred amounts are as disclosed above. The mixing is performed for a sufficient period of time effective to form the flowable composition for use as a controlled release implant. Preferably, the biocompatible thermoplastic polyester and the biocompatible polar aprotic solvent are mixed together to form a mixture and the mixture is then combined with the leuprolide acetate to form the flowable composition.
The present invention also provides for a biodegradable implant formed in situ, in a patient. The biodegradable implant product is prepared by the process of injecting a flowable composition within the body of the patient and allowing the biocompatible polar aprotic solvent to dissipate to produce a solid biodegradable implant. These ingredients, their properties, and preferred amounts are as disclosed above. Preferably, the patient is a human. The solid implant preferably releases the effective amount of leuprolide as the solid implant biodegrades in the patient.
The present invention also provides for a method of forming a biodegradable implant in situ, in a living patient. The method includes injecting the flowable composition of the present invention within the body of a patient and allowing the biocompatible polar aprotic solvent to dissipate to produce a solid biodegradable implant. The flowable composition includes an effective amount of a biodegradable thermoplastic polyester, an effective amount of a biocompatible polar aprotic solvent, and an effective amount of leuprolide acetate. These ingredients, their properties, and preferred amounts are as disclosed above. Preferably, the solid biodegradable implant releases the effective amount of leuprolide acetate by diffusion, erosion, or a combination of diffusion and erosion as the solid implant biodegrades in the patient.
The present invention also provides a method of reducing LH levels in a patient. The method includes administering to the patient in need of such LH reduction an effective amount of a flowable composition of the present invention. Specifically, the reduction of LH levels can be useful to treat endometriosis. In addition, the patient can be a human.
The present invention also provides a method of reducing LHRH levels in a patient. The method includes administering to the patient in need of such LHRH reduction an effective amount of a flowable composition of the present invention. Specifically, the reduction of LHRH levels can be useful to treat endometriosis. In addition, the patient can be a human.
The present invention also provides a kit. The kit includes a first container and a second container. The first container includes a composition that includes the biodegradable thermoplastic polyester and the biocompatible polar aprotic solvent. The second container includes leuprolide acetate. These ingredients, their properties, and preferred amounts are as disclosed above. Preferably, the first container is a syringe and the second container is a syringe. In addition, the leuprolide acetate is preferably lyophilized. The kit can preferably include instructions. Preferably, the first container can be connected to the second container. More preferably, the first container and the second container are each configured to be directly connected to each other.
The present invention also provides a solid implant. The solid implant includes a biocompatible thermoplastic polyester and leuprolide acetate. The biocompatible thermoplastic polyester is at least substantially insoluble in aqueous medium or body fluid. The solid implant has a solid or gelatinous microporous matrix, wherein the matrix is a core surrounded by a skin. The solid implant can further include a biocompatible organic solvent. The biocompatible organic solvent is preferably miscible to dispersible in aqueous or body fluid. In addition, the biocompatible organic solvent preferably dissolves the thermoplastic polyester. The amount of biocompatible organic solvent, if present, is preferably minor, such as from 0 wt. % to about 20 wt. % of the composition. In addition, the amount of biocompatible organic solvent preferably decreases over time. The core preferably contains pores of diameters from about 1 to about 1000 microns. The skin preferably contains pores of smaller diameters than those of the core pores. In addition, the skin pores are preferably of a size such that the skin is functionally non-porous in comparison with the core.